spatstat (version 1.21-2)

MultiHard: The Multitype Hard Core Point Process Model

Description

Creates an instance of the multitype hard core point process model which can then be fitted to point pattern data.

Usage

MultiHard(types, hradii)

Arguments

types
Vector of all possible types (i.e. the possible levels of the marks variable in the data)
hradii
Matrix of hard core radii

Value

  • An object of class "interact" describing the interpoint interaction structure of the multitype hard core process with hard core radii $hradii[i,j]$.

Warnings

The argument types is interpreted as a set of factor levels. That is, in order that ppm can fit the multitype hard core model correctly to a point pattern X, this must be a marked point pattern; the mark vector marks(X) must be a factor; and the argument types must equal levels(marks(X)).

Details

This is a multitype version of the hard core process. A pair of points of types $i$ and $j$ must not lie closer than $h_{ij}$ units apart.

The matrix hradii must be symmetric, with entries which are either positive numbers or NA. A value of NA indicates that no distance constraint should be applied for this combination of types. Note that only the hardcore radii are specified in MultiHard. The canonical parameters $\log(\beta_j)$ are estimated by ppm(), not fixed in MultiHard().

See Also

ppm, pairwise.family, ppm.object, MultiStrauss, MultiStraussHard, Strauss

Examples

Run this code
h <- matrix(c(1,2,2,1), nrow=2,ncol=2)
   MultiHard(1:2, h)
   # prints a sensible description of itself
   data(betacells)
   h <- 15.0 * matrix(c(NA,1,1,NA), nrow=2,ncol=2)
   ppm(betacells, ~1, MultiHard(c("off","on"), h))
   # fit the stationary multitype hardcore process to `betacells'

Run the code above in your browser using DataCamp Workspace